Why does php 'use' fail when I put example code into a function? -

having started example code, don't understand why these scenarios don't work.

script of example code called script.php file works when run command line

<?php //script in standalone file: script.php  //...define stuff require required_file; use aws\ses\sesclient; //now stuff ?> 

when inline contents of script large program fails on 'use' part.

<?php //class-of-bigger-program.php  //function called other part of program function foo(){     //paste contents of same script above     //...define stuff     require required_file;     use aws\ses\sesclient;//crash here     // stuff } ?> 

however when including script in same place of larger program works fine.

<?php //function called other part of program function foo(){     //paste contents of same script above     include 'script.php'; } ?> 

why case? miss using 'use' command? have found differences between 'use' , 'include' , namespaces hard understand.

why add use in function? if class-of-bigger-program.php class, should do:

require required_file;  use aws\ses\sesclient;   class yourclass {...}